Switch



BEST AVNLABLE COP.

March 29 1927,, 1,622,649

H. D. JAGJJ'EEES SWITCH Filed Feb 20. 1920 INVENTOR H [en/:7 D. dameo.

Patented Mar. 29, 1927.

BEST Ai/AILABLE cor.

UNITED STATES PATENT OFFICE. '1

HENRY D. JAMES, OF EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF IENNSYLVANIL SWITCH.

Application filed February 20, 1920. Serial No. 360,115

'My invention relates to switches and it has particular relation to electromagnetically operable switches of the so-called lockout type which close only when the current traversing a selected circuit is below a predetermined value. I

The object of my invention is to provide a switch of the character indicated above in which the effectiveness of the means for actuating the switch to its closed position shall be increased during the closing movement In the operation of electrcmagneticaily operable switches in which opposing forces are exerted upon the movable members, the force tending to close a switch at the instant of the predominance of that force is only slightly greater than the opposing force, since the closing movement is initiated at-that instant. It is obvious, therefore, thattheclosing movement is effected while the resultant force exerted upon the .movable element of the switch is materially less than the normal force exerted by theclosing means. It occurs frequently that such switches close siowly and that the contact members do not make firm engage- .menfi- 1.

..,In a...switch constructed in accordance ,withmyinvention, the closing movement of the switch occurs when the force tending to close the switch predominates over the op- ;posixig force. During the closing movement,.or substantially concurrently with the engagement of the contact members. an air gap between two relatively movable members of the switch is decreased to correspondingly decrease the reluctance of the magnetic circuit for effecting the closing of the .switch. The effectiveness of the force exertedby the actuating coil of the switch is thereby materially increased prior to or concurrently with the actual engagement of the contact members. This arrangement effects a more positive operation of the switch and the result is to prolong the life of thepcoacting contact members by reason I of. their firm engagement.

In theaccompanying drawing, Fig. 1 is a side view, partially in elevation and partially in'section. of a switch embodying my in vention; Figs. 2 and 3 are views of details; Figs. 4and5 are diagrammatic views of circuits and apparatus embodying a plurality of switches of the type shown in Fig. 1.

Referring to Figs. 1, 2, and 3, the base plate 1 of suitable insulating material sup ports a stationary contact member 2. A movable contact member 3 is pivotally supported by and yieldingly connected to a 4' movable arm 4 that is, in turn, pivotally supported at 5 by a stationary member 6. As best shown inFig. 2, thearm 4. is pro vided with an opening 7 which materially reduces the cross-sectional area of the arm and correspondingly increases the reluctance of a magnetic circuit comprising this member. The movable arm 4 constitutes an armature memlienttor an electromagnet 8 comprising a shunt-connected coil 9 and a core member 10. The armaturemember 4 is provided with an extended portion 12 or tail piece of non-magnetic materialwhich engages the member 6 to limit the outward vided. also, with an varm lti ,which coacts with the extension :12 of the armature mem- =ber 4 to limit the relative movements of the arms 4 and 13. The armature member 14 and its connected parts are controlled by anelectromagnet 17 which comprises a coil 18' and a core member 19.- The coil 18.is so connected that it has series characteristics, that 1s. it is responsive to the values :of the current traversing the motor circuit.

The switch is normally in its open posi-.

tion. The coil 9, which may be termed the closing coil, is energized to a substantially constant degree and the electromagnet 8 tends to efiect the engagement of the relatively movable contact members 2 and 3. The coil 18, or lockout coil. isconnected either in series with the motor or in shunt relation to a portion of the starting resistor in such manner as to be energized in accordance with the value of the current traversing the motor circuit. The force exerted hv the electromagnet 17 tending to retain the switch in its open position Varies. theretore. in accordance with the value of the current traversing the motor circuit. As is well known, the value of the current decreases with theaacoeleration otthe motor, other-conditions remaining the same.

It may be assumed that the respective 5 ooils of! the switchxare-electrically connected in thermmendeseribedabove. It may be assumed, further, that the switch is in its open position. The electromagnet 8 exerts a substantially constant force. tending to move the armature member '4 to its closed position. ..The main magnetic circuit of the electromagnet 8 comprises the core member 10, armature -=member 4, and supporting member '6. {As previously stated in connection with the description-0f the structural details of the switch,- the. armature member 4' is'df restricted cross-sectional area and the 'reluctance ofthe main magnetic circuit is accordingly. relatively high.

A leaha-gepath for the 'fiux ot the electromagnet 8. inclu'des the armature member 4, the air gap'between. the armature, member 4:- and the arm'15, the arm15,.an'd supportirig member .6. The .'fiux traversing the leakage path'tends to close. the air gap'between the armature members and the arm 15l1ut such tendency is opposed by. the iorce offthe lelectromagnet 17.

' the value of. the current traversing 'the'sei'ies coil 18 falls to such value that the force exerted by the electromagnet 8 predominatesover that of. the electromagnet 17'5'the armaturemember 4' is actuated to- :war'd its closed position .by a relatively weak force-since, at'theinitiation of such movevme ntfthe opposing forces are .nearly balanced. The closing 'force increases, however, reasdn of the decreasing length of the "arr gapubetween the core member 10 and 40 "thearmature member .41, while the force exerted by the lockout. electromagnet decreases by reason of the increasing length of the corresponding. air gap.

"The approach of'themovable member a to*the core member. 8 causes an increased film: to. traverse the'leakage. path including the arm .15. "An increased force accordingly ten'ds to effect relative movement of the arm 15 and armature member 4 to close the air gap between them. 'Prior to, orsubstan- "'tially concurrent with, the. engagement of .the contact members 2 and 3 and the actuation of the movable member 4 to its closed position, the arm 15 is actuated into engage- :ment with the armature member 4: and the opening'7 is bridged bythearm 15 to materially decrease the reluctance of the main magnetic circuit and thereby insure that the armature memberj i'jis held in' its closed po- .sition by a forcethat, is materially stronger than'that exerted upon it during its closing movement. '.The closing force is also increased to a certain degree by reason ot' theftact that the relative movement of the armature membcr'4 and arm 15 operates to increase the air gap between the armature member 14 and the core-member. 19; thereby decreasing the opposing torce of the electromagnet 17.

It will bereadilyappa-eciated that themrangeinent :whereby. the 7 ull otthe closing electromagnet is materially increased at the instant of engagement of the contact members has the important advantage of effecting their firm engagement and insuring that the movable elements of the switch shall remain in their respective closed positions. The

life of the contact members is increasml since this arrangement removes'theppossibility of the separation, of thecont-a'ct members because of the recoil resulting from the impact of their engagement 'a'ndeliminates the arcing which may result lfrom such separation.

Reference may now be-had to Fig. "Pin which is illustrated a-system-embodying-an electric motor and a plurality ofswitches constructed in accordance'with my invention. An electric motor '21-'having an armature '22 and a 'shnnt"field-magnet=winding 23 is supplied with energy fromline' eonduetors 24 and 25. A sectional starting-resistor. 26 is controlled by a series ef=succe ssively operable switches- 27, 28 v-a'n'd :29 er the lockout type suchas-are shown inF-igs. 1, 2 and 3 and ashave'been'desciibedEin detail above. Similar numerals --are -employed to designate parts corresponding-to those of the switch of 'Fig. 1.

Upon the closing ofthe motor'circuit any suitable means (not show-n) arelat-ively' heavy current traverses'theanain circt'rit including the resistor 26. The shunt closing coil 9 of the switch 27, whichis; connected across the line, is subjected to line-voltage. It will be noteth'however, that theclosing coils 9 of switches 28 and 29"hav e oneterminal connected to intermediate'points'- of the starting resistor 26 and the applied voltage is accordingly less than line voltage. 110 This arrangement insures that the switches operate in the desired sequence. 'The series lockout coils of each of'the several switches are connected in shunt relation to that sec tion of the resistor 2-6 that iscontro'lled by 115 the switch 29 and they are accordingly-energized in accordance Withthe value-ofthe current traversing the motor circuit -,as measured vby the drop in potential across the resistor section.

\Vhen the current fallsto' the predeter- -mined value at which the switch'27 is adapted to operate, the -armature-member 4'. and the arm 15 are moved-toward their closed positions as described abovein connection with the switch of Fig.1. "The engagement of contact members -Qrand' 3 closes a. shunt circuit for the corresponding section of the starting resistor-26.

The shunting of the resistor'seetion 'operates to connect the closing coil S) of switch 28 directly across the line and thereby subject it to full line voltage. When the rush of current incident to the closing of switch 27 decreases to the predetermined value, the switch 28 closes in the manner described in connection with switch 27.

The closing of switch 28 and the shunting of the corresponding resistor section oper ates to apply full line voltage to the closing coil 9 of switch 29 and the latter switch closes when the current traversing the motor circuit falls again to the predetermined value. The shunting of the final section of the starting resistor 26 effects the deenergization of all of the lockout coils l8 and the respective closing coils are, there fore, entirely unopposed with the exception of the force of gravity tending to open the switches.

The system illustrated in Fig. 5 dilfers from that of Fig. 4 in that the series lockout coils are respectively connected in series with the several resistor sections 30 and the armature of the motor. The shunt closing coils are connected by an arrangement that is the equivalent of that of the system of Fig. 4. The operation of the system differs in no material respect from that of the system of Fig. 4 and a detailed description is omitted as being unnecessary to a complete understanding of this portion of my invention.

The many advantages of lockout switches constructed in accordance with my invention, certain of which have been previously fully set forth, will be appreciated by those skilled in the art to which my invention appertains.

I claim as my invention:

1. The combination with a pair of relatively movable coacting contact members, of a movable magnetizable member operatively connected to one of the contact members, a winding adapted to normally exert a closing force on the magnetizable member, a second magnetizable member connected to the first named magnetizable member and movable relatively thereto, a winding adapted to normally exert a force on the second magnetizable member to restrain both mem bers, and means automatically movable to reduce the reluctance of the magnetic circuit through the first named magnetizable member when the magnetic force exerted BEST AVAlLASLE COP thereon exceeds the magnetic force exerted upon the said second magnetizable member.

2. The combination with a pair of relatively movable coacting contact members, of a movable magnetizable member operatively connected to one of the contact members, a winding adapted to normally exert a closing force on the magnetizable member, a second magnctizable member connected to the first named magnetizable member and movable relatively thereto, a winding adapted to normally exert a force on the second magnetizable member in opposition to force exerted thereon through the first magnetizable member, and means controlled by the second named magnetizable member for reducing the reluctance of the magnetic circuit through the first named magnetizable member when the magnetic force exerted thereon exceeds the magnetic force exerted upon said second magnetizable member.

3. The combination with a pair of coacting contact members and a movable member operatively connected to one of said contact members, said member having a magnetizable portion of restricted cross-sectional area, of a second movable member having a magnetizable portion adapted to coact with the other magnetizable portion, electromagnetic means for actuating the first movable member, and electromagnetic means operable, when energized above a predetermined degree, to maintain the separation of said magnetizable portions.

4. The combination with a pair of coacting contact members and a movable member operatively connected to one of said contact members, said member having a magnetizable portion of restricted cross-sectional area, of a second movable member having a magnetizable portion adapted to coact with the other magnetizable portion, electromagnetic means for actuating the first movable member, and eleetro-magnetic means operable, when energized above a predetermined degree, to maintain the separation of said magnetizable portions and, when energized below a predetermined degree, to permit relative movement of said magnetizable portions to increase the effectiveness of the first electromagnetic means.

In testimony whereof, I have hereunto subscribed my name this 10th day of February 192-0. v

' HENRY D. JAMES. 

